Chemistry Chapter 5 Sample Answers - Grade 8 South Africa Exam 2024

Science Exam Paper 8 - Chemistry Answers for Class 8 Students in South Africa, 2024

As students prepare for their science exams in South Africa, they often seek guidance on specific questions related to different chapters of study. This includes understanding concepts such as atoms, elements, compounds, mixtures, states of matter, chemical reactions, and more. In this post, we will focus on Chapter 5, specifically on chemistry topics covered by the Grade 8 South African National Curriculum Statement (NCS) and provide sample answers to help you understand what is expected.

Atoms and Elements

Question: What are atoms? Answer: Atoms are the smallest units of any element that can exist independently. They have three basic properties: mass, charge, and location. Here's how you can remember these properties using the phrase 'Mad, Dad, Lad': Mass means 'Matter', Charge refers to whether it's positive or negative like the poles of a magnet, and Location indicates where the atom is located on the periodic table.

Question: Explain the difference between elements and compounds. Answer: Elements are pure substances made up of only one type of atom. For example, gold has just one kind of atom—gold atoms. Compounds, however, are formed when two or more different types of atoms bond together. Think of it as combining your favorite colors in paint! No single color remains; instead, new colors form together, creating something unique.

Bonds

Question: Name some common ways atoms can share electrons. Answer: There are several ways atoms can share electrons, including covalent bonds, ionic bonds, and coordinate covalent bonds. Covalent bonds involve sharing electron pairs between atoms, while in ionic bonds, one atom loses an electron and becomes positively charged (a cation), attracting another negatively charged atom (an anion). Coordinate covalent bonds involve sharing electron pairs, with one atom contributing both electrons, and the other atom merely accepting them.

Periodic Table

Question: How many groups does the periodic table have? Answer: The periodic table consists of seven horizontal rows called periods, each containing approximately eight columns known as families or groups. Each family contains elements that have similar characteristics because they all have the same number of valence electrons—the outermost electrons available to participate in chemical bonding.

States of Matter

Question: Define the states of matter from solid to gas. Answer: Solids have a fixed size and shape since their particles are closely packed together. Liquids, on the other hand, flow and take the shape of whatever container they're in due to their looser packing of particles. Gases expand into spaces with no particular shape or volume, constantly moving around freely.

Energy Changes During Reactions

Question: Give an example of a physical change versus a chemical reaction. Answer: A physical change involves no chemical bond breaking or forming but may lead to changes in appearance, such as melting ice (solid water turning into liquid) or boiling water (liquid water becoming steam). Conversely, during a chemical reaction, bonds break apart and new ones form, resulting in the formation of products we cannot go back to the starting materials.

By reviewing these key points, you should feel better prepared for your upcoming examination on chemistry topics covered under the Grade 8 NCS curriculum. Remember, practice makes perfect, so keep working through your textbook and past papers to build confidence and knowledge.